Doctors have said that women over the age of 40 may have difficulty conceiving, but a new French study suggests men over the age of 40 are also less fertile, Reuters reports.

The findings were presented at the European Society of Human Reproduction and Embryology conference.

"Our data gives evidence for the first time, for a strong paternal effect on IUI (intrauterine insemination) outcome either on pregnancy rates but also on miscarriage rates," said Stephanie Belloc and her team from the Eylau Centre for Assisted Reproduction in France.

The team looked at samples from more than 21,000 so-called IUI in which the sperm was washed in centrifuge to separate them from seminal fluid and then inserted directly into the uterus.

The sperm’s quality was examined, as were the pregnancies, miscarriages and delivery rates. Researchers found the paternal impact on miscarriages were stronger once the men passed the age of 40.

Older women participating in the study were less likely to get pregnant, but the risk of miscarriage was higher for couples in which the man was over the age of 40.

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